Relatively small low cost electromagnetic switches, often referred to as relays and contactors and hereinafter referred to generally as relays, are well known, with representative examples being illustrated in U.S. Pat. No. 4,112,400 to Jaidinger et al and U.S. Pat. No. 4,423,399 to Goodrich. Such relays find utilization in a variety of applications but typically share several common objectives, including durability, relative compactness, and low cost to manufacture. These relays typically include a stamped, metal yoke or frame member, a magnetic core mounted on the frame member, a coil wound about a bobbin which is in turn disposed about the core, an armature and one or more electrical contacts selectively opened and closed by energization of the coil and resulting actuation of the armature.
More specifically, the frame has typically assumed either a U-shape or more often a L-shape, with a base portion and at least one vertically extending leg portion. The core has been securely mounted to the frame leg portion to extend upwardly in parallel with the frame leg portion. The armature is typically an elongated flat element which is in pivotal engagement with the frame leg portion and is movable relatively toward and away from the upper end of the core. Typically, a spring biases the armature to a position relatively away from the core and energization of the coil serves to draw the armature relatively toward the core. It is common in relays of this type to provide the pivotal mount for the armature by resting one end of the armature on an edge of the frame leg portion, which pivot edge extends in a plane which is substantially parallel to the frame base portion.
In assembling the core to the frame base portion, various mounting techniques have been employed. For example, U.S. Pat. Nos. 3,314,032 to Van Erden and the aforementioned 4,423,399 disclose arrangements in which a screw extends upwardly through an opening in the frame base portion and into threaded engagement with the lower end of the core. An alternate embodiment in the aforementioned U.S. Pat. No. 3,314,032 discloses an arrangement by which the lower end of the core is press-fitted into an opening in the frame base portion. That core includes one or more shoulders which limit the downward insertion of the core by engagement with the base portion. The lower end of the core is shown as being flush with the undersurface of the frame base portion, this result presumably being achieved by precise prepositioning of the core shoulder or by a finishing operation on the core end following insertion. In another example, U.S. Pat. Nos. 2,423,116 to Price and 4,112,400 mentioned earlier, disclose arrangements whereby a narrow stake end at the lower part of the core extends through an opening in the frame base portion and the downwardly projecting end is peened over to rigidly mount the core. In a further example, at least some of the T90 series of relays provided by the Potter and Brumfield Division of AMF, Incorporated, Princeton, Ind. mount the core to the frame base portion by first deforming the metal downward about an opening in the base portion to provide a downwardly extending support collar and then press-fitting the shank portion of a core into the base portion and support collar. A shoulder formed on the core limits downward insertion of the core and also determines the positioning of the top of the core.
While each of the aforementioned arrangements for mounting the core to the frame base may be adequate in accomplishing that general end, each possesses certain limitations which it may be desirable to avoid. Specifically, those constructions which use either a screw, a peened-over head or a downwardly-extruded support collar each include a projecting element on the undersurface of the frame base which may interfere with the smooth mounting of that surface to a support surface or housing.
Further, it is also important that the height of the upper end of the core be precisely established relative to that of the pivot axis or pivot edge of the frame leg portion to obtain the desired electromagnetic dynamics of the device. This objective might be accomplished by careful design and machining of the shoulder near the lower end of the core at which the core stake portion begins to accurately establish the distance from there to the core head. However, it has often been observed that the manufacturing tolerances in machining that shoulder into the core and in the smoothness of the upper surface of the core base portion itself and further in the positioning of the pivot edge in the frame leg portion often accumulate to frustrate such predesign. In such instance, it is even necessary to employ the use of shims about the stake at the base of the core and/or to make the pivot edge overly high on the frame leg and then machine it to the correct height following insertion of the core into the frame base.